E.g. amoxicillin binds first via non-covalent interactions to certain regions of the protein. These initial and fast non-covalent bindings positions the drug favorably to facilitate subsequent covalent binding of the beta-lactam to lysines: The beta-lactam ring opens and binds as amoxicilloyl covalently to lysins in position 190, 432, 525, 541 of the human serum albumin (HSA) (16). The configuration of the bound amoxicillin-HSA (non-covalent) and amoxicilloyl-HSA (covalent) is similar/identical for the reactive IgE antibody.